The Importance of Rule Restrictions in CCG

Marco Kuhlmann, Alexander Koller, and Giorgio Satta. The Importance of Rule Restrictions in CCG. In Proceedings of the 48th Annual Meeting of the Association for Computational Linguistics (ACL), pages 534–543, Uppsala, Sweden, 2010.


Combinatory Categorial Grammar (CCG) is generally construed as a fully lexicalized formalism, where all grammars use one and the same universal set of rules, and cross-linguistic variation is isolated in the lexicon. In this paper, we show that the weak generative capacity of this `pure' form of CCG is strictly smaller than that of CCG with grammar-specific rules, and of other mildly context-sensitive grammar formalisms, including Tree Adjoining Grammar (TAG). Our result also carries over to a multi-modal extension of CCG.